After months of fractious negotiations, KCET, the flagship public broadcasting station in the Los Angeles market for 40 years, abruptly announced Friday that it would exit the PBS network effective Jan. 1. The move, which caught PBS officials in Washington by surprise, marks the first time a major-market station has left the network and will make KCET the largest independent public TV station in the nation.

"This is not a decision we made lightly," Al Jerome, the station's president and chief executive, said in a statement.

"We have been in discussions with PBS for over three years about the need to address challenges that are unique to our market as well as our station."

In a follow-up interview, Jerome said the station would assemble its own programming, a plan that would take roughly two years to implement fully. KCET is expected to keep airing locally produced public-affairs shows such as "SoCal Connected." Last month it announced a new Sunday-night movie show hosted by KTLA entertainment reporter Sam Rubin. Jerome said the station was also exploring news, documentaries and other programming from providers in Japan, Canada and other countries as well as the Hollywood community.

But Jerome acknowledged that some longtime viewers face the immediate prospect of losing favorite, nationally recognized shows. "There are going to be some disruptions," he said. According to Jerome, KCET would remain a nonprofit enterprise mostly reliant on funds from viewers and corporate donors; the station's FCC license does not permit it to become a commercial, for-profit outlet supported entirely by the traditional 30-second spot.

Station officials have complained they could not afford to pay member dues that rocketed 40% after KCET in 2005 won a landmark series of grants from oil giant BP and other sources totaling $50 million for two series aimed at preschoolers. Those grants came with the stipulation the money could not be used for paying dues to PBS. But PBS has defended the dues structure as necessary to maintaining quality programming and argued KCET was asking for special treatment.

Talks aimed at ending the impasse have gone nowhere. The door is still open for KCET to remain tied to PBS through a proposed consortium with Southern California secondary public stations: Orange County's KOCE as well as KVCR in San Bernardino and KLCS, which is licensed to the Los Angeles Unified School District. The group would share certain programming, fundraising and marketing functions to save money and operate more efficiently. But Jerome said KCET would still remain independent under that scenario. It's also possible that the station and PBS could reach an 11th-hour settlement, but those hopes seem to be growing dimmer with each passing day.

Friday's move left PBS officials scrambling. In a sign of how badly relations have frayed with the dissident station, a network spokeswoman was not aware that KCET was about to send out a news release announcing the split until a reporter called to ask about it.

"PBS was notified today of KCET's intention to withdraw its membership," PBS said in a statement. "At issue were KCET's repeated requests that it be allowed to operate as a PBS member station without abiding by PBS policies and paying the corresponding dues.

"PBS' goal is to have a financially stable service in the Los Angeles market," the network added. "PBS fully supports the idea of a Southern California consortium of stations and continues discussion with KOCE, KVCR and KLCS, PBS' additional stations serving the Los Angeles market."

Their divorce could wind up being painful for both KCET and PBS — not to mention local viewers.

The station faces the challenge of trying to raise funds without invoking name brands such as "Sesame Street" and "Antiques Roadshow." Such famous PBS series are frequently cited as reasons to donate during ubiquitous on-air pledge drives. Without such brands, KCET may find it much harder to persuade viewers to open their wallets, especially during a time of economic uncertainty and reduced corporate giving.

However, KCET's prospects for viability could greatly improve if KCET secures funding from the federal government. In a statement released Friday by the Corporation for Public Broadcasting, which receives Congressional funding and distributes it to public media, KCET will still be eligible for federal monies as long as it is — as it plans to be — an FCC-licensed educational television station, providing noncommercial and general interest programming.

In the meantime, the loss of its largest West Coast station casts a dark cloud over the future of PBS, at a time when many TV analysts are already questioning the relevance of a federally mandated broadcasting entity that dates from the 1960s.